Expansion valve for refrigerating cycle

ABSTRACT

An expansion valve for a refrigerating cycle, in which the body dimensions and the weight of the whole valve can be reduced and a reduction in cost can be achieved.  
     An expansion valve of the invention comprising a temperature-sensing portion arranged in a refrigerant passage leading to an evaporator from a gas cooler or an internal heat exchanger in a vapor compression type refrigerating cycle and varied in internal pressure according to a refrigerant temperature at an outlet side of the gas cooler or on an outlet side of the internal heat exchanger, a valve member that mechanically interlocks with a change in internal pressure of the temperature-sensing portion to adjust an opening degree of a valve port, and a body that accommodates therein the valve member, and wherein the body is provided with a flow passage, through which a refrigerant reduced in pressure by the valve member is led to the evaporator while a refrigerant temperature at the outlet side of the gas cooler or on the outlet side of the internal heat exchanger is transmitted to the temperature-sensing portion. Also, that density, at which a refrigerant is charged in a temperature-sensing body, is set in the range of about 200 kg/m 3  to about 600 kg/m 3 . Further, a ratio of a temperature-sensing cylinder corresponding portion to the temperature-sensing body is made at least 60%.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an expansion valve for a refrigeratingcycle that controls a refrigerant on a radiator outlet side on the basisof a refrigerant temperature at the radiator (gas cooler) outlet side ofa vapor-compression-type refrigerating cycle, and is especially suitedto a supercritical refrigerating cycle that uses a refrigerant, such ascarbon dioxide (CO₂) or the like, in a supercritical range.

2. Description of Related Art

Generally, it is known to use, as a vehicular air conditioningapparatus, a vapor-compression-type refrigerating cycle that circulatesCO₂ as a refrigerant in a closed circuit comprising a compressor 1, agas cooler (radiator) 2, an expansion valve 3, an evaporator 4, anaccumulator 5, etc. Conventionally, a pressure control valve asdisclosed in JP-A-2000-193347 and JP-A-2003-254460 is known as amechanical type expansion valve used in such a vapor compression typerefrigerating cycle.

As shown in FIG. 12, the pressure control valves disclosed inJP-A-2000-193347 and JP-A-2003-254460 control a refrigerant pressure atan outlet side of a radiator 2 by passing a refrigerant at an outlet ofa radiator 2 in a casing 30, which covers a valve member part, in whichgases such as refrigerant or the like are charged in an enclosed space Aformed on one side of a diaphragm 32 with the diaphragm therebetween,and a pressure of high pressure refrigerant before pressure reductionacts on the other side to displace the diaphragm 32 to make a valvemember 31 move, and detecting a refrigerant in the enclosed space(temperature-sensing portion) A.

However, the pressure control valve of the conventional type involves aproblem that the weight is increased to lead to an increase in cost asthere is a need for the casing 33 that covers the enclosed space(temperature-sensing portion).

Also, there is also known a pressure control valve (expansion valve) ofa type in which the casing 30 is eliminated to achieve reduction incost, an enclosed space is connected to a temperature-sensing cylinder 7through a capillary tube 6, the temperature-sensing cylinder 7 isprovided in contact with a pipe at an outlet of a radiator 2, and thetemperature-sensing cylinder 7 detects a refrigerant temperature at theoutlet of the radiator 2, but this type of expansion valve involves aproblem of an increase in cost as there is a need of a process ofassembling the temperature-sensing cylinder 7.

Also, the case where CO₂ is used as a refrigerant involves a problemthat the theoretical cycle efficiency is low as compared to HFC134a asconventionally used. Therefore, there is a need of enhancing anefficiency COP of a refrigerating cycle through heat exchange between agas cooler outlet refrigerant and a refrigerant sucked by a compressorwith the use of an internal heat exchanger shown in FIG. 3. When theinternal heat exchanger is used, a sucked refrigerant of the compressoris heated and enthalpy is increased to bring about a superheat state. Inorder to efficiently operate a refrigerating cycle in which arefrigerant, such as CO₂, with high pressure becomes supercritical,there is proposed a construction in which density in an enclosed spaceis prescribed but this takes no account of a refrigerating cycle usingan internal heat exchanger (see JP-A-9-264622).

Further, as a gas cooler outlet refrigerant temperature or an internalheat exchanger outlet refrigerant temperature is detected in a CO₂cycle, a high pressure control valve is arranged in an engine room inthe case where the cycle is applied to a vehicular air conditioningapparatus. As the temperature in the engine room is higher than that ofan outside air and a refrigerant cooled by a gas cooler does not flow tothe control valve when the cycle is stopped, the control valve is heatedto the ambient temperature in the engine room, which is higher than thatof an outside air, and sometimes reaches 100° C. to 120° C.

As a refrigerant is charged in a temperature-sensing portion in thecontrol valve, the pressure in the temperature-sensing portion rapidlyrises when an ambient temperature rises and the charged refrigerant isheated. As a refrigerant temperature at a gas cooler outlet is cooledclose to the ambient temperature, a maximum temperature in the engineroom reaches 30 to 60° C. above a maximum temperature of the refrigerantat the gas cooler outlet. Therefore, the pressure in thetemperature-sensing portion at the time of stoppage becomes higher thana maximum pressure of the CO₂ cycle, so that a very highpressure-resistance, above that for other high pressure parts, isdemanded of the temperature-sensing portion.

In this manner, when the control valve is heated to an ambienttemperature in the engine room, the pressure in the temperature-sensingportion becomes higher than a normal high-pressure control pressure tobring about a valve-closed state at the startup of the CO₂ cycle.Therefore, cooling of the temperature-sensing portion is conventionallyperformed by circulating a small quantity of refrigerant through a bleedhole provided near the valve part and causing the refrigerant cooled bya gas cooler to flow to the control valve. Thereafter, the control valveis opened until temperature of the temperature-sensing portion isdecreased and internal pressure of the temperature-sensing portion isdecreased to a range of high-pressure control pressure, so that therefrigerant is increased in flow rate and a maximum cooling capacity isobtained. Accordingly, in order to reduce the time elapsed until themaximum cooling capacity is attained, that is, cool-down, it becomesimportant to quickly lower the internal pressure of thetemperature-sensing portion to a normal control pressure.

Besides, in a supercritical cycle using CO₂, a refrigerant in atemperature-sensing portion is put in a supercritical state as thetemperature of a refrigerant at a gas cooler outlet, in which highpressure is attained, or an internal heat exchanger outlet is detected.With a conventional HFC134a, a refrigerant in a temperature-sensingportion is used in a gas-liquid two-phase and a refrigerant pressure isdetermined at a saturation temperature, that is, a liquid refrigeranttemperature, so that pressure in the temperature-sensing portion is notaffected by temperatures in other regions. However, a refrigerant put ina supercritical state is affected by temperatures of those regions,which are communicated to and other than the temperature-sensingportion, to cause a problem that the internal pressure of thetemperature-sensing portion is not determined and control pressure isvaried.

SUMMARY OF THE INVENTION

The invention has been made in view of the above problems and has as itsobject to provide an expansion valve for a refrigerating cycle that doesnot need any casing and any temperature-sensing cylinder, can reduce thebody dimensions and the weight of the whole valve and enables areduction in cost. A further object is to provide an expansion valve fora refrigerating cycle that can decrease the pressure-resistance of atemperature-sensing portion by optimizing control characteristics in thecase where an internal heat exchanger is used in combination. A stillfurther object is to provide an expansion valve or a refrigerating cyclecomprising an expansion valve which, when used in a supercritical cycle,decreases variation in control pressure and enables miniaturization ofan expansion valve member.

The invention provides, as means for solving the problem, an expansionvalve for a refrigerating cycle according to the respective claims.

An expansion valve for a refrigerating cycle according to the firstaspect of the present invention is arranged in a refrigerant passageleading from a gas cooler to an evaporator in a vapor compression typerefrigerating cycle, and comprises a temperature-sensing portion, innerpressure of which is varied according to the refrigerant temperature atthe outlet side of the gas cooler, a valve member that mechanicallyinterlocks with a change in internal pressure of the temperature-sensingportion to adjust an opening degree of the valve port, and a body thataccommodates therein the valve member, and the body is provided with aflow passage, through which a refrigerant reduced in pressure by thevalve member is led to the evaporator while the refrigerant temperatureat the outlet side of the gas cooler is transmitted to thetemperature-sensing portion, whereby it is possible to omit a casingthat covers the temperature-sensing portion, or a capillary tube and atemperature-sensing cylinder, into which a refrigerant is introduced,and to achieve miniaturization of the expansion valve and reduction incost.

An expansion valve for a refrigerating cycle according to the secondaspect of the present invention is applied to a vapor compression typerefrigerating cycle provided with an internal heat exchanger, andarranged in a refrigerant passage leading from an internal heatexchanger to an evaporator, the expansion valve comprising atemperature-sensing portion, inner pressure of which is varied accordingto the refrigerant temperature at the outlet side of the gas cooler, avalve member that mechanically interlocks with a change in internalpressure of the temperature-sensing portion to adjust an opening degreeof the valve port, and a body that accommodates therein the valvemember, and wherein the body is provided with a first flow passage,through which a refrigerant flows to the internal heat exchanger, and asecond flow passage, through which a refrigerant reduced in pressure bythe valve member is led to the evaporator from the internal heatexchanger, while the refrigerant temperature at the outlet side of thegas cooler is transmitted to the temperature-sensing portion, whereby itis possible in the same manner as the first aspect to achieveminiaturization of the expansion valve and a reduction in cost.

An expansion valve for a refrigerating cycle according to the thirdaspect of the present invention is applied to a vapor compression typerefrigerating cycle provided with an internal heat exchanger, and isarranged in a refrigerant passage leading from an internal heatexchanger to an evaporator, the expansion valve comprising atemperature-sensing portion, inner pressure of which is varied accordingto the refrigerant temperature at the outlet side of the internal heatexchanger, a valve member that mechanically interlocks with a change ininternal pressure of the temperature-sensing portion to adjust anopening degree of the valve port, and a body that accommodates thereinthe valve member, and wherein the body is provided with a flow passage,through which a refrigerant reduced in pressure by the valve memberflows to the evaporator while the refrigerant temperature at the outletside of the internal heat exchanger is transmitted to thetemperature-sensing portion.

With the expansion valve, the temperature-sensing portion can comprise adiaphragm, and a lid and a lower support member, which interposetherebetween a peripheral edge of the diaphragm from upper and lowerdirections to define an enclosed space above the diaphragm, andtransmission of a refrigerant temperature to the temperature-sensingportion is performed by a clearance, which is formed by the valve memberand the lower support member to be communicated to the refrigerantpassage, whereby it is possible to transmit a refrigerant temperature tothe temperature-sensing portion through the clearance and to omit acasing, or a capillary tube and a temperature-sensing cylinder.

With the expansion valve, the enclosed space of the temperature-sensingportion can be charged with a refrigerant and provided with anadjustment spring, which biases the valve member in a Salve closingdirection, and a valve closing force provided by internal pressure inthe temperature-sensing portion and the adjustment spring and a valveopening force provided by a refrigerant pressure balance to operate thevalve member.

With the expansion valve, the enclosed space of the temperature-sensingportion can be charged with a mixed gas of a refrigerant and gases,which are lower in coefficient of thermal expansion than therefrigerant, and an adjustment spring, which biases the valve member ina valve closing direction, is omitted, whereby it is possible tosimplify the construction and reduced the number of parts.

An expansion valve for a refrigerating cycle according to the fourthaspect of the present invention is one provided with an internal heatexchanger, and has a feature in that a density, at which a refrigerantis charged in the temperature-sensing portion, is 200 to 600 kg/m³ in avalve closed state. Thereby, it is possible to optimize controlcharacteristics when an internal heat exchanger is used, and to decreasepressure-resistance of the temperature-sensing body.

With the expansion valve, the density, at which a refrigerant is chargedin the temperature-sensing portion, can be 200 to 450 kg/m³ in a valveclosed state, whereby it is possible to further optimize controlcharacteristics and to decrease pressure-resistance of thetemperature-sensing body.

With the expansion valve, the valve member can be opened when highpressure at the outlet side of the gas cooler or at the outlet side ofthe internal heat exchanger becomes higher by a predetermined magnitudethan inner pressure in the temperature-sensing portion.

With the expansion valve, a load corresponding to the predeterminedmagnitude can be given by an elastic member, or a non-condensed gascharged in the temperature-sensing portion together with a refrigerant,or the elastic member and the non-condensed gas.

With the expansion valve, the elastic member can be any one of a coilspring, a diaphragm, and a bellows, or an optional combination thereof.

With the expansion valve, when a refrigerant temperature at the outletside of the gas cooler is 50° C. or higher, the internal heat exchangercan heat a refrigerant sucked into a compressor so that superheatbecomes 10° C. or higher.

An expansion valve for a refrigerating cycle according to the fifthaspect of the present invention is one that uses a refrigerant in asupercritical state, and comprises a temperature-sensing portion havinga first enclosed space provided above a diaphragm and charged with arefrigerant, and a second enclosed space provided below the diaphragm tobe communicated to the first enclosed space. Thereby, it is possible toenlarge a volume of the temperature-sensing body and to improve thetemperature-sensing body in accuracy.

With the expansion valve, the second enclosed space can be providedinside a valve member fixed to the diaphragm.

With the expansion valve, the sum of a half of a volume of the firstenclosed space and a volume of the second enclosed space can amount to60% or more of the sum of a volume of the first enclosed space and thesecond enclosed space. Thereby, it is possible to lessen influences oftemperature at a portion of the temperature-sensing portion except thetemperature-sensing cylinder corresponding portion.

The expansion valve can further comprise a lid that covers a wallsurface of the first enclosed space in contact with an outside air toprovide an air layer between the wall surface and the outside air, andcan lessen the influence of the temperature of the outside air.

With the expansion valve, at least a part of the wall surface of thefirst enclosed space in contact with an outside air can be covered by athermal insulating material, and it is possible to further lessen theinfluence of temperature of the outside air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a vapor compression type refrigeratingcycle, in which CO₂ is circulated as a refrigerant;

FIG. 2 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a first embodiment of the invention,used in the refrigerating cycle illustrated in FIG. 1;

FIG. 3 is a view illustrating a vapor compression type refrigeratingcycle including an internal heat exchanger;

FIG. 4 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a second embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 3;

FIG. 5 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a third embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 3;

FIG. 6 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a fourth embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 1 or 3;

FIG. 7 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a fifth embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 3;

FIG. 8 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a sixth embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 1 or 3;

FIG. 9 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a seventh embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 1 or 3;

FIG. 10 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to an eighth embodiment of the invention,applied to the refrigerating cycle illustrated In FIG. 3;

FIG. 11 is a cross sectional view showing an expansion valve for arefrigerating cycle, according to a ninth embodiment of the invention,applied to the refrigerating cycle illustrated in FIG. 3;

FIG. 12 is a cross sectional view showing a conventional expansion valvefor a refrigerating cycle (pressure control valve);

FIG. 13 is a view showing an improvement in COP in the case where aninternal heat exchanger is used;

FIG. 14 is a view showing control pressure, at which COP becomesmaximum, versus a gas cooler outlet temperature when a refrigerant in anevaporator is 0° C.;

FIG. 15 is a view showing control pressure, at which COP becomesmaximum, versus a gas cooler outlet temperature when a refrigerant in anevaporator is 20° C.;

FIG. 16 is a view showing a collier chart representative of physicalproperties Of CO₂ refrigerant;

FIG. 17 is a view schematically showing effects at the time ofcool-down;

FIG. 18 is a view schematically showing a temperature-sensing cylindercorresponding portion of a temperature-sensing body and a portion exceptthe portion;

FIG. 19 is a view (first) showing a change in control pressure versus aratio of a temperature-sensing cylinder corresponding portion;

FIG. 20 is a view (second) showing a change in control pressure versus aratio of a temperature-sensing cylinder corresponding portion; and

FIG. 21 is a view showing an embodiment obtained by providing a lid on atemperature-sensing portion of the ninth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An expansion valve for a refrigerating cycle according to an embodimentof the invention will be described below with reference to the drawings.FIG. 1 is a view illustrating a vapor compression type refrigeratingcycle (supercritical refrigerating cycle), in which CO₂ is circulated asa refrigerant, and FIG. 2 is a cross sectional view showing an expansionvalve for a refrigerating cycle, according to a first embodiment of theinvention, applied to the vapor compression type refrigerating cycleillustrated in FIG. 1. In FIG. 1, the reference numeral 1 denotes acompressor that sucks and compresses a refrigerant (CO₂), and 2 a gascooler (radiator) that cools the refrigerant compressed by thecompressor 1. An expansion valve 3 is arranged on an outlet side of thegas cooler 2 to control a refrigerant pressure at the outlet side of thegas cooler 2 on the basis of a refrigerant temperature at the outletside of the gas cooler 2, the expansion valve also functioning as adecompressor that decompresses a refrigerant at high pressure. In FIG.1, a temperature-sensing cylinder 7 is mounted on an outlet-side pipe ofthe gas cooler 2 and connected to the expansion valve 3 through acapillary tube 6. Accordingly, a valve opening degree of the expansionvalve 3 is controlled according to the change in internal pressure,which is based on a refrigerant temperature of gases charged in thetemperature-sensing cylinder 7.

The reference numeral 4 denotes an evaporator that evaporates agas-liquid two-phase refrigerant decreased in pressure by the expansionvalve 3, and 5 an accumulator that separates a gaseous phase refrigerantand a liquid phase refrigerant from each other and temporarilyaccumulates a surplus refrigerant in the refrigerating cycle. Thecompressor 1, the gas cooler 2, the expansion valve 3, the evaporator 4,and the accumulator 5 are connected together by means of piping to forma closed circuit.

Subsequently, an expansion valve for a refrigerating cycle 3A accordingto the first embodiment will be described with reference to FIG. 2.Formed in a body 33 of the expansion valve 3A is a part of a refrigerantlow passage leading from the gas cooler 2 to the evaporator 4 via avalve port 33 a. Formed in the body 33 are an inflow port 33 b connectedto a side of the gas cooler 2, an outflow port 33 c connected to a sideof the evaporator 4, a first opening 33 d, to which atemperature-sensing portion described later is mounted, and a secondopening 33 e, in which an adjustment spring 36 is set. A valve member 31is received in the body 33 to open and close the valve port 33 a wherebyan upstream space C₁ connected to an outlet side of the gas cooler 2 anda downstream space C₂ connected to an inlet side of the evaporator 4,which spaces are disposed in the body 33, are put into communication andnon-communication to each other.

The temperature-sensing portion is mounted to the first opening 33 d ofthe body 33. The temperature-sensing portion mainly comprises thediaphragm 32, a lid 35, and a lower support member 34, and is formedtherein with an enclosed space A. That is, a concave portion 35 a isformed centrally of the lid 35 to define the enclosed space A, and thelid 35 and the lower support member 34 interpose and secure a peripheraledge of the diaphragm 32 therebetween to form the temperature-sensingportion. The diaphragm 32 is in the form of a thin film made of astainless steel material to be deformed and displaced according to apressure difference inside and outside the enclosed space A. The lowersupport member 34 comprises a cylindrical portion 34 a and a flangeportion 34 b, and a threaded portion formed on an outer periphery of thecylindrical portion 34 a is threaded into the first opening 33 d of thebody 33 to mount the temperature-sensing portion to the body 33. Also, acharge pipe 35 b is mounted to the lid 35 and a refrigerant is chargedinto the enclosed space A through the charge pipe 35 b. After therefrigerant is charged, the charge pipe 35 b is sealed.

One end 31 b of the valve member 31, extending upwardly, of a valveportion 31 a through the cylindrical portion 34 a of the lower supportmember 34 is fixed to the diaphragm 32, and a clearance B having anannular-shaped cross section is formed between an inner surface of thecylindrical portion 34 a and an outer peripheral surface of the valvemember 31. The clearance B is communicated to an upstream space C₁connected to the outlet side of the gas cooler 2. Accordingly, arefrigerant on the outlet side of the gas cooler 2 flows into theclearance B, so that a refrigerant temperature is transmitted to arefrigerant in the enclosed space A and at the same time pressure of therefrigerant on the outlet side of the gas cooler 2 acts on the diaphragm32.

Further, an adjustment nut 37 is threaded onto the other end 31 c of thevalve member 31 extending downwardly of the valve portion 31 a throughthe valve port 33 a. The adjustment spring 36 that biases the valvemember 31 in a valve closing direction is interposed between aneighborhood of an underside of the valve port 33 a and the adjustmentnut 37, and an initial set load (an elastic force in a state, in whichthe valve port 33 a is closed) of the adjustment spring 36 can beoptionally adjusted by rotating the adjustment nut 37. The adjustmentspring 36, the adjustment nut 37, etc. are provided in the downstreamspace C₂ connected to the inlet side of the evaporator 4. Also, a cap 38is fitted into the second opening 33 e of the body 33 whereby a lowerpart of the downstream space C₂ is closed.

With the expansion valve for a refrigerating cycle 3A, according to thefirst embodiment, constructed in the above manner, a valve closing forceof the valve member 31 is provided by inner pressure in the enclosedspace A and the adjustment spring 36, a valve opening force of the valvemember 31 is provided by a refrigerant pressure at the outlet side ofthe gas cooler 2, and balance of the both forces affords opening andclosing the expansion valve 3A. Also, the inner pressure in the enclosedspace A is varied depending upon temperature of that refrigerant on theoutlet side of the gas cooler 2, which flows into the clearance B,whereby the valve port 33 a is varied in opening degree to control therefrigerant pressure at the outlet side of the gas cooler 2.

FIG. 3 is a view illustrating a vapor compression type refrigeratingcycle, in which an internal heat exchanger is incorporated. In thismanner, the vapor compression type refrigerating cycle including aninternal heat exchanger is a conventionally known refrigerating cycle toimprove a cooling capacity. In this case, an internal heat exchanger 8is arranged in the cycle as shown in FIG. 3 so as to make heat exchangebetween a refrigerant going to the expansion valve 3 from the gas cooler2 and a refrigerant returning to the compressor 1 from the accumulator5. Accordingly, the evaporator valve 3 is arranged in a refrigerantpassage leading from the internal heat exchanger 8 to the evaporator 4.The remaining construction is the same as the vapor compression typerefrigerating cycle illustrated in FIG. 1 and so an explanation thereforis omitted. The refrigerating cycle according to the invention is alsoapplicable to a vapor compression type refrigerating cycle includingsuch an internal heat exchanger.

FIG. 4 is a cross sectional view showing an expansion valve for arefrigerating cycle 3B, according to a second embodiment, applied to avapor compression type refrigerating cycle including an internal heatexchanger. A first flow passage D making a part of a refrigerant flowpassage leading from a gas cooler 2 to an internal heat exchanger 8 anda second flow passage E making a part of a refrigerant flow passageleading from the internal heat exchanger 8 to an evaporator 4 via avalve port 33 a, respectively, are formed independently in a body 33 ofthe expansion valve 3B according to the second embodiment. According tothe second embodiment, a clearance B, through which a refrigeranttemperature at an outlet side of the gas cooler 2 is transmitted to arefrigerant in an enclosed space A of a temperature-sensing portion, isprovided on a side of the first flow passage D, and a valve portion 31 aof a valve member 31, which opens and closes the valve port 33 a, isprovided on a side of the second flow passage E.

That is, one end 31 b of the valve member 31 extending upwardly of avalve portion 31 a across the first flow passage D and through acylindrical portion 34 a of a lower support member 34 is fixed to adiaphragm 32, and a clearance B having an annular-shaped cross sectionis provided between an inner surface of the cylindrical portion 34 a andan outer peripheral surface of the valve member 31. The clearance E iscommunicated to the first flow passage D connected to the outlet side ofthe gas cooler 2. Accordingly, a refrigerant on the outlet side of thegas cooler 2 flows into the clearance B, so that the refrigeranttemperature is transmitted to a refrigerant in the enclosed space A andat the same time pressure of the refrigerant on the outlet side of thegas cooler 2 acts on the diaphragm 32.

A valve port 33 a providing for communication between the internal heatexchanger 8 and the evaporator 4 is provided in the second flow passageE. Accordingly, the valve portion 31 a of the valve member 31, whichopens and closes the valve port 33 a, an adjustment spring 36 providedon the other end 31 c of the valve member 31 extending downward throughthe valve port 33 a, an adjustment nut 37, etc. are provided in thesecond flow passage E. The remaining detailed construction is the sameas that of the first embodiment and so an explanation therefor isomitted.

FIG. 5 is a cross sectional view showing an expansion valve for arefrigerating cycle 3C, according to a third embodiment, applied to avapor compression type refrigerating cycle including an internal heatexchanger. According to the third embodiment, a part of a refrigerantflow passage leading from an internal heat exchanger 8 to an evaporator4 via a valve port 33 a is formed in a body 33 of the expansion valve3C. That is, the remaining construction is the same as that of theexpansion valve 3A of the first embodiment except that an inflow port 33b of the body 33 is connected to the internal heat exchanger 8 in placeof a gas cooler 2.

Accordingly, according to the third embodiment, a refrigerant on anoutlet side of the internal heat exchanger 8 flows into a clearance B,so that a refrigerant temperature at the outlet side of the internalheat exchanger 8 is transmitted to a refrigerant charged in an enclosedspace A of a temperature-sensing portion. Likewise, a refrigerantpressure at the outlet side of the internal heat exchanger 8 acts on adiaphragm 32. The same function and effect as those in the firstembodiment are produced also in the third embodiment.

FIG. 6 is a cross sectional view showing an expansion valve for arefrigerating cycle 3D, according to a fourth embodiment, applied to thevapor compression type refrigerating cycle illustrated in FIG. 1 or FIG.3. According to the fourth embodiment, in place of the adjustment spring36, for example, nitrogen gases (N₂), helium gases (He), etc., which arelower in the coefficient of thermal expansion than a refrigerant,together with the refrigerant are charged in an enclosed space A in theexpansion valve according to the first embodiment in FIG. 2 or in theexpansion valve according to the third embodiment in FIG. 5. That is,according to the fourth embodiment, a refrigerant and gases, which arelower in coefficient of thermal expansion than the refrigerant, arecharged in the enclosed space A of the temperature-sensing portion, asecond opening 33 e of a body 33 is closed, and a portion extendingdownwardly of a valve portion 31 a of a valve member 31, an adjustmentspring 36, an adjustment nut 37, etc. are removed. The remainingconstruction is the same as that of the first embodiment or the thirdembodiment and so an explanation therefor is omitted.

Accordingly, according to the fourth embodiment, only inner pressure ofthose mixed gases charged in the enclosed space A, to which temperatureof a refrigerant on the outlet side of the gas cooler 2 flowing into aclearance B is transmitted, acts as a valve closing force of the valvemember 31, and a refrigerant pressure at the outlet side of the gascooler 2 acts as a valve opening force. In this manner, according to thefourth embodiment, gases, which are lower in the coefficient of thermalexpansion than the refrigerant, function as an adjustment spring 36.Also, in the case where a refrigerant is carbon dioxide (CO₂) and thegas being mixed are nitrogen gas (N₂), it is preferred that carbondioxide (CO₂) be charged at a density in the order of 500 to 700 kg/m³and nitrogen gas (N₂) be charged at a density in the order of 10 to 40kg/m³.

FIG. 7 is a cross sectional view showing an expansion valve for arefrigerating cycle 3E, according to a fifth embodiment, applied to avapor compression type refrigerating cycle including the internal heatexchanger shown in FIG. 3. According to the fifth embodiment, as in thefourth embodiment, in place of the adjustment spring 36, for example,nitrogen gas (N₂) helium gas (He), etc., which are lower in thecoefficient of thermal expansion than a refrigerant, together with therefrigerant are charged in an enclosed space A in the expansion valve 3Baccording to the second embodiment. That is, according to the fifthembodiment, a mixed gas of a refrigerant and gases, which are lower incoefficient of thermal expansion than the refrigerant, are charged in anenclosed space A of a temperature-sensing portion, a second opening 33 eof a body 33 is closed, and a portion extending downwardly of a valveportion 31 a of a valve member 31, an adjustment spring 36, anadjustment nut 37, etc. are removed from a second flow passage E. Theremaining construction is the same as that of the second embodiment andso an explanation therefor is omitted.

Accordingly, according to the fifth embodiment, only inner pressure ofthose mixed gases charged in the enclosed space A, to which temperatureof a refrigerant on an outlet side of a gas cooler 2 flowing into aclearance B is transmitted, acts as a valve closing force of the valvemember 31, and a refrigerant pressure at the outlet side of the gascooler 2 acts as a valve opening force. In this manner, according to thefifth embodiment, gases, which are lower in the coefficient of thermalexpansion than the refrigerant, functions as an adjustment spring 36.Also, in the case where a refrigerant is carbon dioxide (CO₂) and thegases being mixed are nitrogen gas (N₂), it is preferred that carbondioxide (CO₂) be charged at a density in the order of 400 to 550 kg/m³and nitrogen gases (N₂) be charged at a density in the order of 10 to 40kg/m³.

FIG. 8 is a cross sectional view showing an expansion valve for arefrigerating cycle 3F, according to a sixth embodiment of theinvention, applied to the refrigerating cycle shown in FIG. 1 or FIG. 3.According to the sixth embodiment, a cavity 31 d communicated to anenclosed space A of a temperature-sensing portion is formed in the valvemember 31 of the expansion valve 3 according to the first embodiment inFIG. 2 or according to the third embodiment in FIG. 5. Accordingly, theenclosed space of the temperature-sensing portion can comprise the sumof (the enclosed space A+the cavity 31 d+the charge pipe 35 b), and theenclosed space charged with a refrigerant can be enlarged, so that it ispossible to improve the temperature-sensing portion in accuracy. Theremaining construction is the same as that of the first embodiment orthe third embodiment and so an explanation therefor is omitted.

FIG. 9 is a cross sectional view showing an expansion valve for arefrigerating cycle 3G, according to a seventh embodiment of theinvention, applied to the refrigerating cycle shown in FIG. 1 or FIG. 3.According to the seventh embodiment, like the sixth embodiment, a cavity31 d communicated to an enclosed space A of a temperature-sensingportion is formed in the valve member 31 of the expansion valve 3according to the fourth embodiment in FIG. 6. Also, according to theseventh embodiment, the enclosed space of the temperature-sensingportion can be further increased by a volume of the cavity 31 d, so thatit is possible to improve the temperature-sensing portion in accuracy.The remaining construction is the same as that of the fourth embodimentand so an explanation therefor is omitted.

FIG. 10 is a cross sectional view showing an expansion valve for arefrigerating cycle 3H, according to an eighth embodiment of theinvention, applied to the refrigerating cycle shown in FIG. 3. Accordingto the eighth embodiment, like the sixth and seventh embodiments, acavity 31 d communicated to an enclosed space A of a temperature-sensingportion is formed in the valve member 31 of the expansion valve 3according to the fifth embodiment in FIG. 7. Also, according to theeighth embodiment, the enclosed space of the temperature-sensing portioncan be further increased by a volume of the cavity 31 d, so that it ispossible to improve the temperature-sensing portion, in accuracy. Theremaining construction is the same as that of the fifth embodiment andso an explanation therefor is omitted.

FIG. 11 is a cross sectional view showing an expansion valve for arefrigerating cycle 3I, according to a ninth embodiment of theinvention, applied to the refrigerating cycle shown an FIG. 3. Accordingto the ninth embodiment, like the sixth, seventh, and eighthembodiments, a cavity 31 d communicated to an enclosed space A of atemperature-sensing portion is formed in the valve member 31 of theexpansion valve 3 according to the second embodiment in FIG. 4. Also,according to the ninth embodiment, the enclosed space of thetemperature-sensing portion can be further increased by a volume of thecavity 31 d, so that it is possible to improve the temperature-sensingportion, in accuracy. The remaining construction is the same as that ofthe second embodiment and so an explanation therefor is omitted.

In addition, while the embodiments have described an expansion valveused for a vapor compression type refrigerating cycle, in which carbondioxide (CO₂) is used as a refrigerant, the expansion valve for arefrigerating cycle according to the invention is not limited theretobut is also applicable to a vapor compression type refrigerating cycle,in which the refrigerant is fluorocarbon or the like, not to mention avapor compression type refrigerating cycle, in which a refrigerant, suchas ethylene, ethane, nitrogen oxide, etc., used in a supercritical zone,is used.

Subsequently, an explanation is given to an embodiment of an expansionvalve suited to a supercritical refrigerating cycle, in which theinternal heat exchanger 8 shown in FIG. 3 is incorporated. The expansionvalve according to the embodiment is intended for firstly, improving COPof a refrigerating cycle including an internal heat exchanger, secondly,enabling decreasing the pressure-resistance of a temperature-sensingportion to achieve reduction in cost, and thirdly, accelerating thecool-down. Therefore, the embodiment prescribes the density at which arefrigerant is charged in a temperature-sensing portion. An explanationis given below.

FIG. 13 shows effects of an improvement in COP in the case where aninternal heat exchanger is used to provide for superheat in a suckedrefrigerant. TS in the figure indicates a refrigerant evaporatingtemperature in an evaporator. Accordingly, the higher a refrigeranttemperature in an evaporator, the higher an improvement in COP. In avehicular air conditioner, a compressor is decreased in rotating speedat the time of idling and a cooling capacity becomes minimum. However,as a refrigerant evaporating temperature in an evaporator rises, COP ofa vehicular air conditioner is enhanced when an internal heat exchangeris used. In this manner, the use of an internal heat exchanger in avehicular air conditioner produces a great advantage.

FIGS. 14 and 15 show high pressure control pressures, at which COPbecomes a maximum, relative to a gas cooler outlet refrigeranttemperature in the case where a refrigerant temperature in an evaporatoris 0° C. and in the case where a refrigerant temperature in anevaporator is 20° C., and show characteristics that in the case where aninternal heat exchanger is used to heat a compressor sucked refrigerant,the lower control pressure in case of possessing superheat, the higher arefrigerant evaporating temperature in an evaporator and the higher agas cooler outlet refrigerant temperature.

This is apparent in the Mollier chart shown in FIG. 16 andrepresentative of physical properties of CO₂ refrigerant. That is, arefrigerant sucked by a compressor ideally follows along an isoentropicline to be compressed to a high temperature high pressure refrigerant.An isoentropic line for the physical properties of CO₂ refrigerant isless inclined as it goes to the right side in the Mollier chart whereenthalpy is increased. This is because, when a comparison is made at thesame pressure, an increase in enthalpy (=compressor power) in case ofcompression to the same pressure becomes large in the case where arefrigerant with superheat is heated, as compared with the case where asaturated gas refrigerant is sucked and compressed.

For a cycle with the use of CO₂ refrigerant, there is known a method ofexercising control to high pressure, at which COP becomes maximum,relative to a gas cooler outlet refrigerant temperature. In case of theprovision of an internal heat exchanger, there is produced an advantagethat a high pressure, at which COP becomes maximum, is decreased since acompressor power is increased. Also, the ability of making a controlpressure low produces an advantage in improving other high-pressureparts such as a compressor, a gas cooler, etc. in durability.

For example, with vehicles, since a traveling wind is not generated atthe time of idling, a gas cooler is decreased in wind velocity, andadditionally a sucked air temperature rises and a gas cooler outletrefrigerant temperature rises due to blowing-in of a hot wind from anengine room. Accordingly, control pressure becomes low in the case wherean internal heat exchanger is used.

Accordingly, in order to make effective use of a refrigerating cycle, inwhich an internal heat exchanger is used, there is a need for ahigh-pressure control valve having control characteristics that controlpressure is further decreased for the same gas cooler outlet refrigeranttemperature. Also, it is necessary to charge a refrigerant into acontrol valve having such characteristics at a lower density than thatat which a refrigerant is charged into a conventionaltemperature-sensing portion (see JP-A-9-264622).

As seen from FIG. 15, assuming that a refrigerant temperature in anevaporator is 20° C. and superheat of a sucked refrigerant is 10° C. ina refrigerating cycle, in which an internal heat exchanger having asmall heat exchanging capacity is used, COP assumes a maximum value whena refrigerant temperature at a gas cooler outlet is 60° C. and controlpressure is 15 MPa. In order to make a control pressure attain 15 MPa,it is necessary to adopt a charged refrigerant density (hereinaftercalled a charging density) in the order of about 600 kg/m³.

Since COP is improved when an internal heat exchanger having a largeheat exchanging capacity is used, it is conceivable to increase aquantity of superheat further. As a discharge temperature also riseswhen a sucked refrigerant temperature of a compressor becomes high,however, a quantity of superheat is preferred to be in the range of 15to 25° C. In case of adopting a quantity of superheat in the range of 15to 25° C., COP becomes maximum in the case where control pressure ismade 14.2 MPa, for example, when a gas cooler outlet refrigeranttemperature is 60° C. In order to make a control pressure attain 14.2MPa, it is necessary to adopt a charging density in the order of about570 kg/m³.

Also, as that density, at which a refrigerant is charged in atemperature-sensing portion of an expansion valve, is desirably low interms of pressure-resistance of the expansion valve described later,inner pressure in the temperature-sensing portion is set low by about 2MPa by further using in combination a spring for biasing the valve in avalve closing direction whereby control pressure, at which COP becomesmaximum, can be ensured even in a charging density in the order of about450 kg/m³ when a gas cooler outlet refrigerant temperature is 60° C.Subsequently, an explanation is given to pressure-resistance of atemperature-sensing portion. As pressure in the temperature-sensingportion at the time of stoppage of a vehicle becomes very high, a largepressure-resistance is required. As is apparent from the Mollier chartof CO₂ refrigerant shown in FIG. 16, the higher a density, the morerapid pressure rises relative to temperature, so that in order todecrease an increase in internal pressure of a temperature-sensingportion, it is necessary to lower a charging density. In particular,there is caused a problem that since an inclination of an isothermalline intersecting an equidensity line becomes is large when the chargingdensity exceeds 600 kg/m³, an increase in internal pressure relative totemperature rise becomes also large.

Also, since a maximum allowable pressure of high-pressure parts is setto about 18 MPa, an upper limit of pressure in a temperature-sensingportion is made in the same order as the pressure to eliminate the needof excessively heightening only the temperature-sensing portion instrength to enable making the same equal to other high-pressure parts instrength, thus enabling providing a control valise at low cost.

Therefore, while it is required that a temperature-sensing portioncharging density be set to at most about 550 kg/m³ when a maximumambient temperature is 80° C., at most about 450 kg/m³ when a maximumambient temperature is 100° C., and at most about 360 kg/m³ when amaximum ambient temperature is 120° C., it is desired that the chargingdensity be set to at most 450 kg/m³ since 100° C. at the highest must betaken account of even when a position of low temperature is selected asa mount position in an engine room.

Further, since a charging density for an intended control pressure canbe reduced by a quantity corresponding to a spring load by giving a loadin a direction of closure with the use of a spring or the line, it iseffective to use the spring or the like in combination.

When a temperature-sensing portion charging density is made small,control pressure for a gas cooler outlet refrigerant temperature isdecreased but the control pressure, at which COP becomes maximum, isalso decreased in case of using an internal heat exchanger, so that theuse of the internal heat exchanger makes it possible to decrease thatdensity, at which a refrigerant is charged in a temperature-sensingportion of an expansion valve, without decreasing COP.

In addition, as shown in the Mollier chart in FIG. 16, a tendency isdemonstrated, in which an inclination of the isothermal line becomesrapidly small and a change in enthalpy become large relative to pressurechange when temperature and pressure of a refrigerant come near to acritical point. Since a quantity of discharged heat is decreased and acooling capacity is decreased when enthalpy at a gas cooler outletincreases, it is desired that, for example, high pressure at 40° C. ofrefrigerant temperature be equal to or higher than 9 MPa (T point inFIG. 16).

Even when a method of giving an initial load by means of a spring or thelike is used in combination, a decrease in cooling capacity becomesconspicuous unless inner pressure in a temperature-sensing portion whenat 40° C. is set to be 7 MPa or higher (at 2 MPa corresponding to aspring load). Accordingly, the temperature-sensing portion chargingdensity is desirably 200 kg/m³ or higher.

Finally, an explanation is given to an acceleration of cool-down. Asdescribed above, at the start of CO₂ cycle, cooling of atemperature-sensing portion is performed by circulating a small quantityof refrigerant through a bleed hole provided near a valve part andcausing the refrigerant cooled by a gas cooler to flow to a controlvalve, and the control valve is opened when the temperature-sensingportion is decreased in temperature and internal pressure of thetemperature-sensing portion is decreased to a range of high-pressurecontrol pressure. Accordingly, in order to accelerate cool-down, itbecomes important to quickly lower the internal pressure of thetemperature-sensing portion to a normal range of control pressure. Inorder to quickly lower the internal pressure of the temperature-sensingportion to a normal range of control pressure, it is effective to use aninternal heat exchanger to set a control pressure to a little low and todecrease that density, at which a refrigerant is charged in atemperature-sensing portion of a mechanical type control valve.

FIG. 17 schematically shows effects at the time of cool-down. When arefrigerating cycle is stopped, an expansion valve in an engine room isheated to high temperature, for example, about 80° C. When therefrigerating cycle is started in this state, the valve is closedbecause the internal pressure of a temperature-sensing portion exceedsan upper limit pressure (in this case, 13 MPa) in operation of thecycle. Therefore, a small quantity of refrigerant cooled by a gas coolerflows through a bleed hole provided near a valve part to cool thetemperature-sensing portion. At this time, a compressor is varied incapacity so as not to exceed the upper limit pressure in operation, thuscontrolling high pressure.

When the temperature-sensing portion is decreased in temperature and theinternal pressure thereof becomes equal to or lower than the upper limitpressure in operation, the valve is opened and the compressor becomesmaximum in capacity, so that the refrigerant is increased in flow rateand a maximum cooling capacity is demonstrated.

When that density, at which the refrigerant is charged in thetemperature-sensing portion, is high, there is a need for cooling to afurther low temperature as compared with the case where the chargingdensity is low, in order that the internal pressure of thetemperature-sensing portion become equal to or lower than the upperlimit pressure in operation. Thus time (=time, during which therefrigerant is small in flow rate), during which the temperature-sensingportion is cooled at the start, is prolonged and a decrease in blow-offtemperature is delayed.

According to the embodiment, the above is taken into consideration andan optimum value of a temperature-sensing portion charging density in arefrigerating cycle, in which an internal heat exchanger is used, isprescribed in the following manner.

Typically, in the expansion valve 3I used in a refrigerating cycleprovided with the internal heat exchanger according to the ninthembodiment illustrated with reference to FIG. 11, that density, at whicha refrigerant is charged into the enclosed space A of thetemperature-sensing portion of the expansion valve 3I, is set in therange of about 200 kg/m³ to about 600 kg/m³. In the case where aquantity of superheat is to be increased, an upper limit value of therange of charging density may be made in the order of about 570 kg/m³,and in the case where an elastic member for biasing in a valve closingdirection is used in combination, the charging density can be made inthe order of about 450 kg/m³. More desirably, that density, at which arefrigerant is charged into the temperature-sensing portion of theexpansion valve, is set in the range of about 200 kg/m³ to about 450kg/m³.

Further, for the expansion valve 3H used in a refrigerating cycle, inwhich the internal heat exchanger according to the seventh embodimentand illustrated with reference to FIG. 10 is used, the expansion valvebeing provided with no adjustment spring, it is preferable to adopt acharged refrigerant density being the same as that described above. Thatis, that density, at which a refrigerant is charged into the enclosedspace A of the temperature-sensing portion of the expansion valve 3H andthe cavity 31 d, is set in the range of about 200 kg/m³ to about 600kg/m³. In the case where a quantity of superheat is to be increased, anupper limit value in the range of charging density may be made in theorder of about 570 kg/m³ and, further, in the case where an elasticmember for biasing in a valve closing direction is used in combination,the charging density can be in the order of about 450 kg/m³. Moredesirably, that density, at which a refrigerant is charged into thetemperature-sensing portion of the expansion valve, is set in the rangeof about 200 kg/m³ to about 450 kg/m³.

Also, in a refrigerating cycle, in which the internal heat exchangeraccording to the second, third, and fifth embodiments (FIGS. 4, 5, and7) is provided, and a refrigerating cycle, in which the internal heatexchanger according to the fourth, sixth, and seventh embodiments (FIGS.6, 8, 9) is provided, that density, at which a refrigerant is chargedinto the temperature-sensing portion of the expansion valve, is set inthe range of about 200 kg/m³ to about 600 kg/m³. In the case where aquantity of superheat is to be increased, an upper limit value in therange of charging density may be in the order of about 570 kg/m³ and,further, in the case where an elastic member for biasing in a valveclosing direction is used in combination, the charging density can bemade in the order of about 450 kg/m³. More desirably, that density, atwhich a refrigerant is charged into the temperature-sensing portion ofthe expansion valve, is set in the range of about 200 kg/m³ to about 450kg/m³.

Subsequently, an explanation is given to those embodiments, which solvea problem that control pressure is varied in a temperature-sensingportion, in which a refrigerant in a supercritical state is used.

As shown in FIGS. 8 to 11, according to the sixth to ninth embodiments,the cavity 31 a being an enclosed space is formed below the diaphragm soas to be communicated to the enclosed space A of the temperature-sensingportion formed above the diaphragm 32. Consequently, the enclosed spaceof the temperature-sensing portion is enlarged to the enclosed spaceA+the cavity 31 d from a conventional enclosed space A. In addition,while the charge pipe 35 b is separated from the enclosed space in theforegoing explanation, it is included in the enclosed space A in thiscase. Accordingly, it can be said that the temperature-sensing portionaccording to the sixth to ninth embodiments comprises the enclosed spaceA and the cavity 31 d. As described above, the cavity 31 d increases avolume of the enclosed space, in which a refrigerant is charged, andimproves the temperature-sensing portion in accuracy.

The enclosed space A is a flat space formed above the diaphragm,temperature of a refrigerant is transmitted to the enclosed spacethrough the diaphragm, and an outer wall of the enclosed space Acontacts with an outside air to be susceptible to influences of anoutside air temperature. Accordingly, it can be said in the constructionof the temperature-sensing portion that, the portion to whichtemperature of a refrigerant is transmitted and which is heated, thatis, the cavity 31 d below the diaphragm and a lower half of the enclosedspace A in contact with the diaphragm correspond to atemperature-sensing cylinder, and an upper half of the enclosed space Asusceptible to influences of an outside air temperature, corresponds toanother portion different from the temperature-sensing cylinder.Accordingly, by attaching an insulating material to the outer wallportion, temperature variation of the upper half of the enclosed space Ais lessened to enable ensuring a minimum temperature-sensing volume.

According to the embodiment, a ratio of the portion (here, the lowerhalf of the enclosed space A and the cavity 31 d) corresponding to thetemperature-sensing cylinder to the whole temperature-sensing portion isprescribed to lessen variation in control pressure.

FIG. 18 schematically shows a temperature-sensing cylinder correspondingportion P and another portion Q. FIG. 19 shows temperature effects ofthe portion Q versus a ratio of the portion P to a whole volume, thatis, a volume ratio of a direct temperature-sensing portion P/(P+Q) forthe temperature-sensing cylinder corresponding portion P and anotherportion Q in the case where the charged refrigerant density assumes astandard value of 450 kg/m³ and temperature of the portion P is 60° C.Temperature of the portion Q is 65° C., 70° C., and 80° C. A targetcontrol pressure is one in the case where temperature of the portion Qis 60° C. to be the same as that of the portion P.

For example, at a point S in FIG. 19 the portion P is at 60° C., theportion Q is at 60° C., a volumetric ratio of the portion P is 50% (theratio of 0.5), the refrigerant density at the portion P is 538 kg/m³,the refrigerant density at the portion Q is 362 kg/m³, internalpressures of the both balance at 13.51 MPa, and an average density is450 kg/m³. A point S indicates pressures balance at the respectivetemperatures and the volumetric ratio.

In this manner, in the case where a refrigerant is in a supercriticalstate, control pressure for the expansion valve is varied by an ambienttemperature in the engine room being affected by temperature of otherportions than the temperature-sensing cylinder corresponding portion.Accordingly, it is necessary to lessen influences of temperature ofother portions than the temperature-sensing cylinder correspondingportion.

Therefore, according to the embodiment, the volumetric ratio of thetemperature-sensing cylinder corresponding portion is ensured, whichamounts to a predetermined magnitude or more. Further, an insulatingmaterial may be attached to the other portion than thetemperature-sensing cylinder corresponding portion to prevent heatingdue to an ambient temperature.

While the larger a difference between a refrigerant temperature and anambient temperature, the more conspicuous influences of the volumetricratio, it is necessary to decrease a change in control pressure in orderto avoid an abnormally high pressure because control pressure becomesalso high and a margin for an upper limit pressure of the cycle is smallIn the case where a gas cooler outlet temperature is high.

While it is desired that the variation in pressure be small, it isnecessary to make the variation equal to or less than about 0.5 MPa inorder to make the same in the order of dispersion in a pressure sensoror the like, and assuming that a maximum temperature of a gas cooleroutlet refrigerant is 60° C. and temperature in the engine room is 80 to100° C., the outer wall portion above the diaphragm rises 5 to 6° C. intemperature even in the case where an insulating material is attachedthereto. Accordingly, in order to rake the variation equal to or lessthan about 0.5 MPa, it suffices to ensure a volume of at least 50% atthe minimum for the volumetric ratio of the temperature-sensing cylindercorresponding portion as seen from FIG. 19.

In the case where a gas cooler outlet refrigerant temperature is low,the control pressure is low so that there is a margin for an upper limitpressure in the cycle. Since a temperature difference between therefrigerant temperature and an ambient temperature becomes large, theinfluence of the ambient temperature becomes large.

FIG. 20 shows effects of temperature of the portion Q (other than thetemperature-sensing cylinder corresponding portion) due to an ambienttemperature in the case where a refrigerant temperature is 40° C. 50°C., 60° C., 80° C., and 100° C. are shown for temperature of the portionQ. A target control pressure is attained when temperature of the portionexcept the temperature-sensing portion is 40° C. While for example, whena refrigerant temperature is 40° C., temperature of the outer wall risesabout 10° C. to attain 50° C. in the case where a temperature differencebetween the refrigerant temperature and an ambient temperature isincreased to 60° C., it is found desirable to make the volumetric ratioof the temperature-sensing cylinder equal to or more than 60% in orderto make variation in high pressure equal to 0.5 MPa.

Also, it can be seen from FIG. 20 that when the volumetric ratio is madeequal to or more than 70%, variation in control pressure can be madeequal to about 0.5 MPa even when an insulating material is omitted forthe portion except the temperature-sensing cylinder correspondingportion.

Accordingly, the larger the ratio to the whole temperature-sensingportion is made by increasing a volume (the lower half of the enclosedspace above the diaphragm and the enclosed space below the diaphragm) ofthe temperature-sensing cylinder corresponding portion, the smaller thevariation in operating value, due to an ambient temperature, can bemade. According to the embodiment, the volumetric ratio of thetemperature-sensing cylinder corresponding portion to the enclosed spaceis made equal to or more than 60%. In addition, the volumetric ratio inthe embodiment is represented by the following formula(Vu×0.5+Vb)/(Vu−Vb)>0.6where Vu indicates a volume of the enclosed space above the diaphragmand Vb indicates a volume of the enclosed space below the diaphragm.

Typically, the expansion valve 3G, according to the seventh embodiment,used in a refrigerating cycle with no internal heat exchanger,illustrated with reference to FIG. 9 is formed such that the volumetricsum of ½ of the enclosed space A (including the charge pipe 35 b) andthe cavity 31 d amounts to at least 60% of the volumetric sum of theenclosed space A (including the charge pipe 35 b) and the cavity 31. Inaddition, while the embodiment is directed to an expansion valve used ina refrigerating cycle with no internal heat exchanger, it may be appliedto a refrigerating cycle with an internal heat exchanger.

Further, the expansion valve, according to the sixth, eighth, and ninthembodiments illustrated with reference to FIGS. 8, 10, 11 can also beformed such that the volumetric sum of ½ of the enclosed space A(including the charge pipe 35 b) and the cavity 31 amounts to at least60% of the volumetric sum of the enclosed space A (including the chargepipe 35 b) and the cavity 31 d.

Further, as shown in FIG. 21, variation in control pressure can besuppressed in the expansion valve 31, according to the ninth embodiment,shown in FIG. 11 by providing a lid 39, which covers the cuter wall ofthe temperature-sensing portion and the charge pipe 35 b, and forming anair layer between the outer wall of the temperature-sensing portion andan outside air to thermally insulate a portion except thetemperature-sensing cylinder corresponding portion of thetemperature-sensing portion.

As described above, according to the invention, as a refrigeranttemperature is transmitted to an interior of the enclosed space Athrough the clearance B, it is possible to omit a casing or a capillarytube and a temperature-sensing cylinder, which are used in the relatedart, and to achieve miniaturization and lightening of an expansion valveand reduction in cost. By composing gases, which are charged in anenclosed space, of mixed gas of a refrigerant and gases which are lowerin the coefficient of thermal expansion than the refrigerant, it ispossible to omit an adjustment spring or the like and to furthersimplify an expansion valve. Also, by prescribing that the density, atwhich a refrigerant is charged into a temperature-sensing body, it ispossible to optimize control characteristics when an internal heatexchanger is used, and to decrease pressure-resistance of thetemperature-sensing body. Further, as a ratio of a temperature-sensingbody to a whole temperature-sensing cylinder corresponding portion isprescribed, it is possible to lessen the partial influences oftemperature of the temperature-sensing body.

1. An expansion valve for a refrigerating cycle, arranged in arefrigerant passage leading from a gas cooler to an evaporator in avapor compression type refrigerating cycle to adjust an opening degreeof a valve port on the basis of a refrigerant temperature at an outletside of the gas cooler to thereby control a refrigerant pressure at theoutlet side of the gas cooler, the expansion valve comprising atemperature-sensing portion, the inner pressure of which is variedaccording to the refrigerant temperature at the outlet side of the gascooler, a valve member that mechanically interlocks with a chance ininternal pressure of the temperature-sensing portion to adjust anopening degree of the valve port, and a body that accommodates thereinthe valve member, and wherein the body is provided with a flow passage,through which a refrigerant reduced in pressure by the valve member isled to the evaporator while the refrigerant temperature at the outletside of the gas cooler is transmitted to the temperature-sensingportion.
 2. The expansion valve for a refrigerating cycle according toclaim 1, wherein the temperature-sensing portion comprises a diaphragm,and a lid and a lower support member, which interpose therebetween aperipheral edge of the diaphragm from upper and lower directions todefine an enclosed space above the diaphragm, and transmission or arefrigerant temperature to the temperature-sensing portion is performedby a clearance, which is formed by the valve member and the lowersupport member to be communicated to the refrigerant passage.
 3. Theexpansion valve for a refrigerating cycle according to any one of claim1, wherein the enclose, space of the temperature-sensing portion ischarged with a refrigerant and provided with an adjustment spring, whichbiases the valve member in a valve closing direction.
 4. The expansionvalve for a refrigerating cycle according to any one of claim 1, whereinthe enclosed space of the temperature-sensing portion is charged with amixed gas of a refrigerant and gases, which are lower in coefficient ofthermal expansion than the refrigerant, and an adjustment spring, whichbiases the valve member in a valve closing direction, is omitted.
 5. Theexpansion valve for a refrigerating cycle according to any one of claim1, further comprising a lid that covers a wall surface of the firstenclosed space in contact with an outside air to provide an air layerbetween the wall surface and the outside air.
 6. The expansion valve fora refrigerating cycle according to any one of claim 1, wherein at leasta part of the wall surface of the first enclosed space in contact withan outside air is covered by a thermal insulating material.
 7. Anexpansion valve for a refrigerating cycle arranged in a refrigerantpassage leading from an internal heat exchanger to an evaporator in avapor compression type refrigerating cycle to adjust an opening degreeof a valve port on the basis of a refrigerant temperature at an outletside of the gas cooler to thereby control a refrigerant pressure at theoutlet side of the gas cooler, the expansion valve comprising atemperature-sensing portion, the inner pressure of which is variedaccording to the refrigerant temperature at the outlet side of the gascooler, a valve member that mechanically interlocks with a change ininternal pressure of the temperature-sensing portion to adjust anopening degree of the valve port, and a body that accommodates thereinthe valve member, and wherein the body is provided with a first flowpassage, through which a refrigerant flows to the internal heatexchanger, and a second flow passage, through which a refrigerantreduced in pressure by the valve member is led to the evaporator fromthe internal heat exchanger, while the refrigerant temperature at theoutlet side of the gas cooler is transmitted to the temperature-sensingportion.
 8. The expansion valve for a refrigerating cycle according toclaim 7, wherein the temperature-sensing portion comprises a diaphragm,and a lid and a lower support member, which interpose therebetween aperipheral edge of the diaphragm from upper and lower directions todefine an enclosed space above the diaphragm, and transmission of arefrigerant temperature to the temperature-sensing portion is performedby a clearance, which is formed by the valve member and the lowersupport member to be communicated to the refrigerant passage.
 9. Theexpansion valve for a refrigerating cycle according to any one of claim7, wherein the enclosed space of the temperature-sensing portion ischarged with a refrigerant and provided with an adjustment spring, whichbiases the valve member in a valve closing direction.
 10. The expansionvalve for a refrigerating cycle according to any one of claim 7, whereinthe enclosed space of the temperature-sensing portion is charged with amixed gas of a refrigerant and gases, which are lower in coefficient ofthermal expansion than the refrigerant, and an adjustment spring, whichbiases the valve member in a valve closing direction, is omitted. 11.The expansion valve for a refrigerating cycle according to any one ofclaim 7, further comprising a lid that covers a wall surface of thefirst enclosed space in contact with an outside air to provide an airlayer between the wall surface and the outside air.
 12. The expansionvalve for a refrigerating cycle according to any one of claim 7, whereinat least a part of the wall surface of the first enclosed space incontact with an outside air is covered by a thermal insulating material.13. An expansion valve for a refrigerating cycle arranged in arefrigerant passage leading from an internal heat exchanger to anevaporator in a vapor compression type refrigerating cycle to adjust anopening degree of a valve port on the basis of a refrigerant temperatureat an outlet side of the internal heat exchanger to thereby control arefrigerant pressure at the outlet side of the internal heat exchanger,the expansion valve comprising a temperature-sensing portion, innerpressure of which is varied according to the refrigerant temperature atthe outlet side of the internal heat exchanger, a valve member thatmechanically interlocks with a change in internal pressure of thetemperature-sensing portion to adjust an opening degree of the valveport, and a body that accommodates therein the valve member, and whereinthe body is provided with a flow passage, through which a refrigerantreduced in pressure by the valve member flows to the evaporator whilethe refrigerant temperature at the outlet side of the internal heatexchanger is transmitted to the temperature-sensing portion.
 14. Theexpansion valve for a refrigerating cycle according to claim 13, whereinthe temperature-sensing portion comprises a diaphragm, and a lid and alower support member, which interpose therebetween a peripheral edge ofthe diaphragm from upper and lower directions to define an enclosedspace above the diaphragm, and transmission of a refrigerant temperatureto the temperature-sensing portion is performed by a clearance, which isformed by the valve member and the lower support member to becommunicated to the refrigerant passage.
 15. The expansion valve for arefrigerating cycle according to any one of claim 13, wherein theenclosed space of the temperature-sensing portion is charged with arefrigerant and provided with an adjustment spring, which biases thevalve member in a valve closing direction.
 16. The expansion valve for arefrigerating cycle according to any one of claim 13, wherein theenclosed space of the temperature-sensing portion is charged with amixed gas of a refrigerant and gases, which are lower in coefficient ofthermal expansion than the refrigerant, and an adjustment spring, whichbiases the valve member in a valve closing direction, is omitted.
 17. Amexpansion valve for a refrigerating cycle arranged in a refrigerantpassage leading to an evaporator from a gas cooler through an internalheat exchanger in a vapor compression type refrigerating cycle to adjustan opening degree of a valve port on the basis of a refrigeranttemperature at an outlet side of the gas cooler or a refrigeranttemperature at an outlet side of the internal heat exchanger to therebycontrol a refrigerant pressure at the outlet side of the internal heatexchanger, the expansion valve comprising a temperature-sensing portioncharged with a refrigerant and varied in inner pressure according to therefrigerant temperature at the outlet side of the gas cooler or therefrigerant temperature at the outlet side of the internal heatexchanger, and a valve member that mechanically interlocks with a changein internal pressure of the temperature-sensing portion to adjust anopening degree of the valve port, and wherein the density, at which arefrigerant is charged in the temperature-sensing portion, is 200 to 600kg/m³ in a valve closed state.
 18. The expansion valve for arefrigerating cycle according to claim 17, wherein the density, at whicha refrigerant is charged in the temperature-sensing portion, is 200 to450 kg/m³ in a valve closed state.
 19. The expansion valve for arefrigerating cycle according to claim 17, wherein the valve member isopened when high pressure at the outlet side of the gas cooler or at theoutlet side of the internal heat exchanger becomes higher, by apredetermined magnitude, than inner pressure in the temperature-sensingportion.
 20. The expansion valve for a refrigerating cycle according toclaim 19, wherein a load corresponding to the predetermined magnitude isgiven by an elastic member, or a non-condensed gas charged in thetemperature-sensing portion together with a refrigerant, or the elasticmember and the non-condensed gas.
 21. The expansion valve for arefrigerating cycle according to claim 20, wherein the elastic membercomprises any one of a coil spring, a diaphragm, and a bellows, or anoptional combination thereof.
 22. The expansion valve for arefrigerating cycle according to claim 17, wherein when a refrigeranttemperature at the outlet side of the gas cooler is 50° C. or higher,the internal heat exchanger heats a refrigerant sucked into a compressorso that superheat becomes 10° C. or higher.
 23. An expansion valve for arefrigerating cycle that uses a refrigerant in a supercritical state,the expansion valve comprising a temperature-sensing portion having afirst enclosed space provided above a diaphragm and charged with arefrigerant, and a second enclosed space provided to be communicated tothe first enclosed space, and wherein a refrigerant on an outlet side ofa gas cooler, or a refrigerant on an outlet side of an internal heatexchanger is introduced below the diaphragm to apply high pressure belowthe diaphragm, a refrigerant temperature at the outlet side of the gascooler, or a refrigerant temperature at the outlet side of the internalheat exchanger is transmitted to a refrigerant charged in thetemperature-sensing portion, and the valve is opened and closed by thatdisplacement of the diaphragm, which is caused by a pressure differencebetween above and below the diaphragm.
 24. The expansion valve for arefrigerating cycle according to claim 23, wherein the second enclosedspace is provided inside a valve member fixed to the diaphragm.
 25. Theexpansion valve for a refrigerating cycle according to claim 23, whereinthe sum of a half of a volume of the first enclosed space and a volumeof the second enclosed space amounts to 60% or more of the sum of avolume of the first enclosed space and the second enclosed space. 26.The expansion valve for a refrigerating cycle according to any one ofclaim 23, further comprising a lid that covers a wall surface of thefirst enclosed space in contact with an outside air to provide an airlayer between the wall surface and the outside air.
 27. The expansionvalve for a refrigerating cycle according to any one of claim 23,wherein at least a part of the wall surface of the first enclosed spacein contact with an outside air is covered by a thermal insulatingmaterial.